The present invention relates to inner filters for an aquarium with an electric motor operating to circulate water in the aquarium.
An inner filter of this type is disclosed for example in the German document DE-GM 81 26 762.2. It is substantially rod-shaped and has an upper pump head which is closed with a cover and accommodates the complete electric motor with a stator and a rotor as well as their bearing axles and bearings for a pump wheel rotated by the rotor. The pump head is also provided with a pump chamber and a pressure passage. The electric motor with its components is fixedly installed in the pump head. The pump chamber and the pump wheel arranged in it are located under the stator and the rotor. A housing part is arranged under the pump head and has a central suction passage which is coaxial to the rotor and can be defined for example by a pipe provided with openings. At least one filter insert is mounted on the pipe. The housing part which contains the filter insert is provided with openings in its wall for suction of water so that the water can be sucked through the filter insert into the central pipe which forms the suction passage. From there the water is supplied by the pump through the pump chamber into the pump head and from the pump head in the pressure passage located in it. Through the pressure passage the water is guided upwardly until it exits from an upwardly located outlet opening from the pump head. In this inner filter the lower end of the bearing axle is held in a special bottom part which is placed from below and releasably on the pump head and which is located between the pump head and the housing part located under it and containing the filter insert. When it is necessary to clean this known inner filter, it must be removed from the aquarium tank as a whole and then dismounted. For exchanging the filter insert the lower tubular housing part can be withdrawn. When, however, for example the pump wheel, the neighboring region of the rotor, the region of the pump chamber or the pressure passage must be cleaned, then first the bottom-side closure of the pump head must be released and removed. Then the rotor with the bearing axle and the bearings must be disassembled in its individual components so that an assembly problem takes place. Moreover, the individual regions even with the removed rotor with the pump wheel are difficult to access and therefore difficult to clean.